Feb. 22, 2012 -- New research shows that colonoscopy saves lives not only by identifying colon cancers early, but also by detecting and removing colon polyps in their precancerous stage.

Removal of the tumor-like growths known as adenomatous polyps was associated with a 50% reduction in expected colon cancer deaths in the largest and longest follow-up of polyp patients ever conducted.

Published in the New England Journal of Medicine, the study confirms what has long been suspected, says researcher Ann G. Zauber, PhD, a biostatistician at Memorial Sloan-Kettering Cancer Center in New York City.

“You would expect to reduce deaths from colorectal cancer when you remove the adenomas that cause them, but we really haven't had the data to prove it until now,” she says, adding that the findings support current colorectal cancer screening recommendations.

Polyp Removal Cut Deaths by Half

The study included slightly more than 2,600 patients with precancerous colon polyps removed during colonoscopy screenings.

The patients were followed for an average of about 16 years after having the procedure, with the longest follow-up being 23 years.

Four out of five patients also had additional surveillance and colonoscopy procedures, as recommended.

Often, a follow-up colonoscopy is recommended three to five years after polyps are removed. The time interval recommended for a repeat colonoscopy varies and is based on several factors, such as the number and type of polyps found.

In the study population, detection and removal of the polyps was associated with a 53% reduction in death from colon cancer compared to expected deaths in the general population of similar age and gender.

Durado Brooks, MD, MPH, director of the American Cancer Society's prostate and colorectal cancer division, says the findings are in line with smaller studies suggesting that polyp removal and surveillance can cut colorectal deaths in half.

“This research provides solid data to confirm this,” he tells WebMD. “But it is not all good news. Even though the death rate was reduced by half, people in this group still died of colorectal cancer.”

Twelve of the patients died of the cancer an average of about a decade (the range was six to 22 years) after having polyps removed during colonoscopy. Five of these fatal cancers were diagnosed during follow-up surveillance.

“Colonoscopy is an extraordinary tool, but it is not infallible,” Brooks says. “Once a polyp is found, people need to be rechecked on a regular basis.”

Screening methods that search for evidence of blood in the stool must be done every year.

“When I'm asked which test is best, the answer I always give is that the best test is the one that gets done,” he tells WebMD.

The ACS recommends colorectal cancer screening beginning at age 50 for both men and women with an average risk for developing colorectal cancer. People with a family history of the disease or other risk factors should begin screenings earlier.

Winawer says at a time when the value of many cancer screening tests is being questioned, the new findings are reassuring.

“The most common outcome of screening colonoscopy is the identification and removal of polyps, and if we remove polyps we prevent cancer and save lives,” he says.